Between 5-10% of adults worldwide suffer from depression. Even more experience depression-related mood disorders such as dysthymia, seasonal affective disorder, and postpartum depression, bipolar disorder, anxiety disorder, posttraumatic stress disorder, panic disorder, and obsessive-compulsive disorder.
The economic costs to society, and person costs to individuals and families, associated with depression are enormous. Within a 15-month period after having been diagnosed with depression, sufferers are four times more likely to die as those who do not have depression. Almost 60% of suicides have their roots in major depression, and 15% of those admitted to a psychiatric hospital for depression eventually kill themselves. See Nierenberg, Am J Manag Care 7(11 Suppl): S353-66, 2001. In the U.S. alone, the estimated economic costs for depression exceeded $44 billion in 1990. The World Health Organization estimates that major depression is the fourth most important cause worldwide of loss in disability-adjusted life years, and will be the second most important cause by 2020.
A variety of pharmacologic agents are available for the treatment of depression. Significant success has been achieved through the use of seratonin reuptake inhibitors (SRIs), norepinephrine reuptake inhibitors (NERIs), combined serotonin-norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs), phosphodiesterase-4 (PDE4) inhibitors or other compounds. However, even with these options available, many patients fail to respond, or respond only partially to treatment. Additionally, many of these agents show delayed onset of activity, so that patients are required to undergo treatment for weeks or months before receiving benefits. Most currently available antidepressants take 2-3 weeks or more to elicit a response.
Traditional therapies can also have significant side effects. For example, more than a third of patients taking SRIs experience sexual dysfunction. Other problematic side effects include gastrointestinal disturbances, often manifested as nausea and occasional vomiting, agitation, insomnia, weight gain, onset of diabetes, prolongation of the heart rate corrected interval (QTc), agranylocytosis, etc. Depressive patients who also suffer from psychotic disorders (e.g., schizophrenia) also sometimes suffer extrapyramidal side effects. These side effects often discourage patients from following their recommended therapeutic regimen.
There remains a need for the development of improved therapies for the treatment of depression and/or other mood disorders.